Multistage hydrothermal quartz veins record the ore-forming fluid evolution in the Meiling Cu–Zn (Au) deposit, NW China

We performed a detailed analysis of hydrothermal quartz at the Mokrsko gold deposit (Čelina, Mokrsko-East, and Mokrsko-West deposits). Twenty-one samples were studied by scanning electron microscopy cathodoluminescence (CL) imagining, CL emission spectra and trace elements were measured on six selected samples. Four quartz growth generations Q1 to Q4 were described. Homogeneous early blue CL Q1 with initial emission spectra at 380 and 500 nm was observed at the Čelina deposit with typical titanium concentrations in the range of 20–50 ppm. Hydrothermal quartz at Mokrsko-West, which also includes early Q1, late subhedral faces of yellow CL Q2, and microfissures of greenish CL Q3 (both 570 nm), is characterized by titanium depletion. The titanium concentration is comparable to previous studies of crystallization temperatures proving titanium concentration in quartz as a good geothermal indicator. Q4, developed in microfissures only at Čelina, has no visual CL effect. Mokrsko-West is specific in comparison to Mokrsko-East and Čelina by germanium enrichments in hydrothermal quartz (up to 17 ppm) and the presence of fluorite. Tectonic (sheeted veinlets system, regional tectonic setting) and geochemical (germanium in quartz, the presence of fluorite) characteristics of the quartz veins link the late mineralization stages at the Mokrsko-West deposit to the temporally related Blatná intrusive suite.

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Two generations of garnets and their relevance for the hydrothermal fluid evolution of the Hongyuntan deposit, NW China

Ore Geology Reviews ◽

10.1016/j.oregeorev.2020.103513 ◽

2020 ◽

Vol 122 ◽

pp. 103513

Author(s):

ZhiYuan Sun ◽

JingBin Wang ◽

YuWang Wang ◽

LingLi Long ◽

QiTao Hu ◽

...

Keyword(s):

Hydrothermal Fluid ◽

Nw China ◽

Fluid Evolution ◽

Two Generations

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Archaean precious-metal hydrothermal systems, Dome Mine, Abitibi Greenstone Belt. II. REE and oxygen isotope relations

Canadian Journal of Earth Sciences ◽

10.1139/e79-041 ◽

1979 ◽

Vol 16 (3) ◽

pp. 440-458 ◽

Cited By ~ 122

Author(s):

R. Kerrich ◽

B. J. Fryer

Keyword(s):

Oxygen Isotope ◽

Greenstone Belt ◽

Precious Metal ◽

Igneous Rocks ◽

Lode Gold ◽

Quartz Veins ◽

Hydrothermal Quartz ◽

Abitibi Greenstone Belt ◽

Chemical Sediments ◽

Gold Bearing

The Porcupine District, Abitibi Greenstone Belt, is one of the most extensive areas of Archaean auriferous mineralisation. At least two stages of lode-gold emplacement are recognised: the first stage involves gold-bearing carbonate–chert chemical sediments within the lower mafic volcanic sequence; the second stage is represented by auriferous hydrothermal quartz veins which postdate deformation of the greenstone assemblage and transect diverse host rocks.Rare-earth element (REE) concentrations in the stratiform carbonates are typical of the distinctive patterns recorded for Archaean chemical sediments. Chert in these rocks has a δ18O value averaging 17.1‰, implying exchange from heavier 18/16 ratios during diagenesis and metamorphism. Metabasic volcanic rocks and quartz–feldspar porphyry stocks with background gold abundances have mean whole-rock δ18O values of 9.1‰ and 10.7‰ respectively. This enrichment in 18O relative to primary igneous rocks is attributed to oxygen isotope exchange with seawater at low temperatures during fluid transport through the oceanic crust.Quartz in all of the five hydrothermal vein systems present has a δ18O of 14‰ to 15‰, and quartz-muscovite fractionations are 3.4‰ to 3.8‰. Ambient temperatures of mineralisation are estimated to have been 400 °C to 450 °C, from oxygen isotope thermometers, fluid inclusion filling temperatures, and metamorphic mineral assemblages. The calculated δ18O of the mineralising solutions is~10‰, implying fluids of metamorphic origin. REE patterns in hydrothermal quartz veins suggest that they have been derived from high-temperature solutions in equilibrium with source rocks having relatively flat (chondrite normalised) REE distributions, such as tholeiitic and komatiitic volcanics. Adjacent to hydrothermal veins, quartz in igneous rocks approaches isotopic equilibrium with vein quartz, at 15‰, and whole-rock δ18O values for metabasalts shift to ~11‰, implying extensive water-rock interaction. Strong depletions in heavy REE of metabasic schists adjacent to veins provides further evidence for pervasive hydrothermal alteration. The Eu enrichment of all lode gold deposits analysed at Dome Mine is consistent with the reduced state of the solutions involved in their deposition, as recorded by the predominance of Fe2+. The gold-bearing veins are believed to have formed by focussed flow of fluids outgassed at the greenschist–amphibolite transition. Source volumes for Au in the Porcupine District exceed 600 km3, the carrier fluid volume for mineralisation was 60–90 km3, the Au solute concentration in the low nanogram mL−1 range, and transport distances were of the order of 10 km. Such veins may be the precursors of precious-metal-bearing chemical sediments if fluids debouche into the hydrosphere.

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Primary Minerals and Age of The Hydrothermal Quartz Veins Containing U-Mo-(Pb, Bi, Te) Mineralization in the Majerská Valley near Čučma (Gemeric Unit, Spišsko-Gemerské Rudohorie Mts., Slovak Republic)

Minerals ◽

10.3390/min11060629 ◽

2021 ◽

Vol 11 (6) ◽

pp. 629

Author(s):

Štefan Ferenc ◽

Martin Števko ◽

Tomáš Mikuš ◽

Stanislava Milovská ◽

Richard Kopáčik ◽

...

Keyword(s):

Electron Microprobe ◽

Slovak Republic ◽

Mineral Phase ◽

Quartz Veins ◽

Hydrothermal Quartz ◽

Ti Oxides ◽

Mineral Phases ◽

Gemeric Unit ◽

Primary Minerals

An occurrence of vein U-Mo mineralization is located in the Majerská valley near Čučma, about 7 km to the NNE of the district town of Rožňava (Eastern Slovakia). Mineralization is hosted in the acidic metapyroclastics of the Silurian Bystrý Potok Fm. (Gemeric Unit), and originated in the following stages: (I.) quartz I, fluorapatite I; (II.) quartz II, fluorapatite II, zircon, rutile chlorite, tourmaline; (III.) uraninite, molybdenite, U-Ti oxides; (IV.) pyrite I, ullmannite, gersdorffite, cobaltite; (Va.) galena, bismuth, tetradymite, joséite A and B, Bi3(TeS)2 mineral phase, (BiPb)(TeS) mineral phase, ikunolite; (Vb.) minerals of the kobellite–tintinaite series, cosalite; (VI.) pyrite II; (VII.) titanite, chlorite; and (VIII.) supergene mineral phases. The chemical in-situ electron-microprobe U-Pb dating of uraninite from a studied vein yielded an average age of around 265 Ma, corresponding to the Guadalupian Epoch of Permian; the obtained data corresponds with the age of Gemeric S-type granites. The age correlation of uraninite with the Gemeric S-type granites and the spatial connection of the studied mineralization with the Čučma granite allows us to assume that it is a Hercynian, granite-related (perigranitic) mineralization.

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